New development in the Grothendieck archives, unfortunately articles are behind paywall.

We know about the 28,000 pages he left to the Universite of Montpellier.

Turns out there are 70,000 additional pages in a cellar in Paris.It is quite unclear what is going to happen to these, they may be auctioned off, with french institution/libraries likely be priced out of the auction by others.